A widely used type of membrane switch assembly comprises a substrate, a membrane which extends parallel to the substrate, and a separator which is between the opposed surfaces of the membrane and the substrate. Circuit conductors and switch sites are provided on the opposed surfaces and frequently, either the membrane or the substrate will be provided with an integral tail onto which the circuit conductors extend. The switch can then be connected to external circuits by means of a connector which would be coupled to the end portions of the conductors on the tail.
It is necessary, in the manufacture of membrane switches as described above, to provide insulating material on the circuit conductors on the tail in a manner such that these conductors will be insulated excepting for portions thereof which function as contact portions and which are engaged with conductors in a connector or the like. The insulation provided on the tail may take the form of a separate insulating layer which is bonded to the tail or other forms. In any event, the provision of the insulating layer to the tail always adds an additional step to the manufacturing process and greatly increases the cost of producing the membrane switch assembly. The present invention is directed to the achievement of an improved membrane switch assembly having an integral tail and a tail insulator which can be manufactured without the necessity of a separate manufacturing step to provide insulation on the surface of the tail.
A membrane switch assembly in accordance with the invention has three parallel layers, the three layers comprising first and second parallel insulating supports having opposed first and second surfaces and a spacer between the first and second surfaces. At least one of the supports is a flexible layer. Opposed switch electrodes are provided at switch sites on the first and second surfaces and openings are provided in the spacer at the switch sites. Circuit conductors are provided on the one support which is a flexible layer and extend between and among the switch electrodes on the one support. An integral tail extends from the one support, the tail having a free end and having an end portion which is adjacent to the free end. The circuit conductors have lead portions which extend onto one surface of the tail and substantially to the free end of the tail. A tail insulator is provided in covering and insulating relationship to the lead portions, the tail insulator extending to the end portion of the tail so that contact portions of the lead conductors, on the end portion of the tail, are exposed. The membrane switch assembly is characterized in that the assembly comprises a second flexible layer, the second flexible layer being one of the layers other than the flexible layer which has the integral tail. The second flexible layer has an integral tail insulator extending therefrom, the tail insulator being substantially co-extensive with the tail and being in covering relationship to the one surface of the tail. The tail insulator has a free end and an opening is provided in the tail insulator adjacent to the free end. The free end of the tail is threaded through the opening and the end portion of the tail extends beyond the opening and beside the other surface of the tail whereby the contact portions only of the lead portions of the conductors are exposed. The second flexible layer may be the spacer or the other support.
In accordance with further embodiments, the tail and the tail insulator have opposed edges at the opening in the tail insulator. The opposed edges prevent movement of the tail insulator along the tail towards the second flexible layer whereby the tail and the tail insulator are maintained in side-by-side relationship with the tail insulator in covering relationship to the lead portion of the conductors. The opening in the tail insulator may be a slot that extends normally of the side edges of the tail insulator.
In accordance with a further embodiment, the tail is of reduced width and has a shoulder directed towards the free end of the tail and the slot in the tail insulator has a width which is substantially equal to the width of the end portion of the tail. The opposed edges are then the shoulder and edges of the slot. An alternative embodiment is characterized in that the end portion of the tail has a constricted width portion which is spaced from the free end of the tail, the constricted width portion being positioned in the slot in the tail insulator and the opposed edges being on the constricted width portion and the slot.
An alternative embodiment of the invention comprises a substrate, a membrane extending parallel to the substrate, a spacer between the membrane and the substrate, and a covering layer in covering relationship to the membrane. The substrate is flexible and has an integral tail extending therefrom. Switch electrodes are provided on the opposed surfaces of the substrate and the membrane, and circuit conductors are provided on the substrate. The circuit conductors extend between and among the switch electrodes on the substrate and have lead portions which extend onto one surface of the tail and to the free end thereof. The lead portions have contact portions on an end portion of the tail which extends from a location adjacent to the free end of the tail to the free end thereof. A tail insulator is provided on the tail extending only to the end portion so that the contact portions are exposed. The membrane switch assembly is characterized in that the tail comprises an integral extension of the covering layer and is substantially co-extensive with the tail. The tail insulator has a free end which is adjacent to the free end of the tail. An opening is provided in the tail insulator adjacent to the free end of the tail insulator and the free end of the tail is threaded through the opening. The end portion of the tail extends beyond the opening and beside the other surface of the tail whereby the contact portions only of the lead portions of the conductors are exposed.